Cities around the world are filled with streets that are no longer streets. It isn’t too hard to spot the diagonal, no-longer-street “street” in the above photo because of its clear impact to the surrounding buildings.
If you zoom in then you see that the diagonal “street” isn’t actually a street, but building shapes, property lines or other forms of outdoor areas (like a car park).
These ghost streets – or ghost structures – are also a good metaphor for something you’ll find in software systems. Previous design decisions aren’t always re-assessed – too many to re-assess all of them – and especially if you are replacing an existing system, then it becomes very difficult to re-design the new system, because it must by necessity integrate with all the other systems (and it is a lot of work to re-work all of those).
The net result is that your new system with the new architecture and design is not as new as you think.